The invention relates to a weldable, corrosion-resistant, high-magnesium content aluminum-magnesium alloy, which contains a ternary aluminum-scandium-zirconium phase as an essential component. Such an alloy is disclosed in U.S. Pat. No. 5,624,632, for application in aerospace construction due to its low density, high strength and corrosion resistance. Adding rare earth or rare earth-like elements generates dispersoids in the aluminum-magnesium alloy, which produce a higher strength and corrosion resistance. The aforesaid U.S. patent is silent as regards the weldability of such an alloy.